Frequency estimation techniques are used to synchronize the clock in communication systems. The clock received with the communication has a frequency offset from the internal clock of the receiver. Determining the offset and adjusting the internal clock by the frequency offset is necessary to achieve good performance in a communication system.
Frequency estimation at low signal to noise ratio (SNR) is needed for modern coding schemes. However, frequency estimation often has a threshold effect at low SNR. As the SNR decreases, a significant degradation of performance of the system occurs.
High performance frequency estimation is often complex, due to the number of calculations necessary, and non-recursive.
Classical optimum frequency estimators employ system data to compute a periodogram by Fourier transforming the signal using, for example, discrete fourier transform (DFT). Getting an accurate estimate using this method requires computation of a large number of frequency points. Such an estimator is suitable for one-shot block processing.
Known estimators apply either single-shot DGFT processing or simplified recursive processing.
One example of a simplified recursive processor has been discussed, for example, by Umberto Mengali, wherein an estimator chooses the value with the greatest frequency, and recomputes the estimator each time.
In order to accommodate the performance and costs associated with synchronization applications, a low complexity recursive formulation is needed.